ExpoImaging ExpoDisc 2.0 77mm White Balance FilterThe 77mm ExpoImaging ExpoDisc 2. 0 White Balance Filter features 18% calibrated light transmission for ensuring correct exposure and white balance settings while shooting and editing. It attaches to lenses or filters with a 77mm thread via a button activated spring attachment. This is even compatible with low profile filter threads. Also, the ExpoDisc 2. 0 can be used with smaller lenses by simply holding the filter in front of the lens. The ExpoDisc